Problems in expressive language create significant barriers in cognitive and social development and in long- term outcomes, such as the ability to live independently. There is significant variability in spoken language in children with autism spectrum disorders (ASD) (Kjelgaard & Tager-Flusberg, 2001; Paul, 2007; Tager- Flusberg, 2004), ranging from an absence of functional verbal communication to relatively spared productive language. Understanding the source of deficits in spoken language is crucial, as productive skill is a key predictor of developmental outcome in this population (Venter et al. 1992). This project directly addresses a critical problem in the study of ASD; heterogeneity in language functioning. One candidate source of the observed heterogeneity in language is the poor modulation of gaze to faces of others in children with ASD (e.g., Hobson et al., 1988; Klin et al., 2002). This limited gaze to the face may have cascading effects on language learning by reducing 1) access to the visible aspects of a speaker's articulations and 2) the likelihood of imitation of visible speech gestures. In the current proposal, sensitive neurobiological and behavioral techniques including electroencephalography (EEG), event related potentials (ERP) and eye tracking will be paired with novel speech tasks to provide a window on the factors that underlie the perception, integration and production of audiovisual speech in children with ASD. In addition, while typically developing children do not exhibit difficulty with social or language functioning, some children share deficits in language with children with ASD, but do not exhibit primary deficits in social reciprocity. Thus, we will compare children with ASD relative to both a group of expressive language-matched and a group of age-matched controls, which will allow us to tease apart the contribution of linguistic and social factors to problems in language functioning. By examining AV speech perception at school-age, when linguistic outcome is known, we provide a potential marker of language function to identify young children who are at particular risk for severe deficits in later language development. This research will expand our understanding of the neurobiological underpinnings of both perception and imitation of AV speech, which have important implications for the acquisition of spoken language.